The present invention relates to semiconductor device fabrication and, more specifically, to bipolar junction transistors, fabrication methods for bipolar junction transistors, and design structures for a bipolar junction transistor.
Bipolar junction transistors are typically found in demanding types of integrated circuits, especially integrated circuits for high-frequency applications. One application for bipolar junction transistors is in radiofrequency integrated circuits (RFICs), which are used in wireless communications systems, power amplifiers in cellular telephones, and other types of high speed integrated circuits. Bipolar junction transistors may also be combined with complementary metal-oxide-semiconductor (CMOS) field effect transistors in bipolar complementary metal-oxide-semiconductor (BiCMOS) integrated circuits, which take advantage of the positive characteristics of both transistor types in the construction of the integrated circuit.
Conventional bipolar junction transistors are three-terminal electronic devices that include three semiconductor regions, namely an emitter, a base, and a collector. Generally, a bipolar junction transistor includes a pair of p-n junctions, namely a collector-base junction and an emitter-base junction. A voltage applied across the emitter-base junction of a bipolar junction transistor controls the movement of charge carriers that produce charge flow between the collector and emitter regions of the bipolar junction transistor.
An NPN bipolar junction transistor includes two regions of n-type semiconductor material constituting the emitter and collector, and a region of p-type semiconductor material sandwiched between the two regions of n-type semiconductor material to constitute the base. A PNP bipolar junction transistor has two regions of p-type semiconductor material constituting the emitter and collector, and a region of n-type semiconductor material sandwiched between two regions of p-type semiconductor material to constitute the base.
Improved devices, fabrication methods, and design structures are needed for bipolar junction transistors that extend the capabilities of the technology.